As the method of detecting interaction between nucleic acid and protein, there is conventionally known a so-called fluorescent method given in Patent Document 1 described below. This method includes labeling both a nucleic acid and a protein with fluorescent stain different from each other and measuring on whether the fluorescent stain act mutually to change the fluorescence to detect an interaction between the nucleic acid and the protein.
The fluorescent method requires a pretreatment process having several stages for specifically staining the nucleic acid and the protein with the fluorescent molecules, thus taking a great deal of time and labor before an actual measurement process. Besides, the fluorescent molecules may affect an active region.
As the method of detecting interaction between molecules without the need of labeling with the fluorescent molecules or the like, an SPR (surface-localized plasmon resonance) sensor can be employed. This method includes bonding a sample in a solid phase onto a metal thin-film formed on a substrate and detecting an absorption degree of the sample, using the SPR sensor, when a predetermined laser beam is incident on the sample.
However, this method is practically hard to be utilized for detecting nucleic acid-protein interaction. The method requires control of the thickness of the metal thin-film in the order of nanometer, and further requires absorption of a molecule for capturing a target molecule called “analyte” (e.g., an antibody to an antigen) into the surface of the thin-film, which makes it extremely hard to create a highly-reproducible substrate. Particularly in measuring a functional molecule, an active region needs to be placed near the surface of a substrate, thus possibly being subjected to influence of the substrate.    Patent Document 1: Japanese Patent Laid-Open Publication No. 2004-16132